Hi, I can't answer you question in particular (someone else probably can) but I did find this great video regarding hair made by Andrew Brown.
https://vimeo.com/88711732 [vimeo.com]
I found the Blender technique works well for guide hairs. (around 41min into video) Personally, I feel that I have better control of the guide hairs using Blender compared to Houdini. (especially for long hair)
hope that helps
Rob
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Houdini Learning Materials » Grooming hair guide? select guides?
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- robsdesign
- 236 posts
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Houdini Learning Materials » Load textures using a single file string
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- robsdesign
- 236 posts
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Thanks for your help.
I knew it was something simple but I was using underscores.
I'll see if I can cope without using underscores for everything and look at the other option if (when) that fails.
thanks
Rob

I'll see if I can cope without using underscores for everything and look at the other option if (when) that fails.
thanks
Rob
Houdini Learning Materials » Load textures using a single file string
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- robsdesign
- 236 posts
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Hi, I'm not sure of the exact terminology so I'll try to explain my question.
I have a set of shader nodes with names matching the texture set. ie. Engine shader has 4 texture maps. Engine_Base, Engine_Roughness, etc.
When working with a lot of textures, I have a fairly simple (but tedious) workflow of copying the name from the shader node and pasting into each file string for the maps.
What I'd like to do is use 1 file string for each map that looks at the name of the shader and appends _Base, _Roughness etc.
ie.
$HIP/tex/“somethingsimplebutclever”_Base.png
$HIP/tex/“somethingsimplebutclever”_Roughness.png
etc
I'd be very grateful if someone can enlighten me.
thanks
Rob
I have a set of shader nodes with names matching the texture set. ie. Engine shader has 4 texture maps. Engine_Base, Engine_Roughness, etc.
When working with a lot of textures, I have a fairly simple (but tedious) workflow of copying the name from the shader node and pasting into each file string for the maps.
What I'd like to do is use 1 file string for each map that looks at the name of the shader and appends _Base, _Roughness etc.
ie.
$HIP/tex/“somethingsimplebutclever”_Base.png
$HIP/tex/“somethingsimplebutclever”_Roughness.png
etc
I'd be very grateful if someone can enlighten me.

thanks
Rob
Technical Discussion » Error running Python code to access the help manager
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- robsdesign
- 236 posts
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Thanks for your reply.
I just tried what you suggested but still have the same problem. (Works for Shelf tools but not for anything else)
When trying the above, it also produced a string of errors in the Houdini console (not just the python error like original post) so I've reverted to the original Environment Variables file.
Maybe the above will work for the others having the same issue but for me it doesn't so I welcome any further suggestions.
I'm not really sure if I should be sending a bug report for this or if it's something wrong with my setup that's causing it. I assume it's working for the vast majority?
Rob
UPDATE: This issue has been fixed in build 15.0.416
I just tried what you suggested but still have the same problem. (Works for Shelf tools but not for anything else)
When trying the above, it also produced a string of errors in the Houdini console (not just the python error like original post) so I've reverted to the original Environment Variables file.
Maybe the above will work for the others having the same issue but for me it doesn't so I welcome any further suggestions.
I'm not really sure if I should be sending a bug report for this or if it's something wrong with my setup that's causing it. I assume it's working for the vast majority?
Rob
UPDATE: This issue has been fixed in build 15.0.416
Technical Discussion » Start-up time
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- robsdesign
- 236 posts
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Thanks for your reply.
I do have a hybrid setup so that does make sense and I've experienced the same in other software too.
Three things confused me enough to ask the initial question…
1. The quick start-up when launching new builds. Next time I update to a new build, I'll make sure to restart pc before I launch to confirm.
2. I was positive the start-up time for early H14 builds was very quick. (or much quicker than 1min 45)
3. I remember seeing a bug fix in the Journal for slow start-up time and wondered if the bug had resurfaced.
I could be wrong on all the above as I'm relying on my memory, which is not so reliable.
I know the answer to the next question will vary a lot depending on system setup but what is the expected start-up time for Houdini on a HDD? There's quite a big gap between 4 sec and 1min 45 so if I know a ballpark figure of where it's supposed to be, I can either stop worrying or dive deeper.
I've also found that when I try clearing the cache in Houdini, it doesn't release the RAM so I need to restart Houdini. Restarting Houdini when this happens also causes the long start-up. (the cache is overwritten?) Is there is a way for me to control how Houdini uses memory for sims so it doesn't overwrite the cache used for the “quick launch”.
Rob
UPDATE: Confirmed odd behaviour. Installed new build, first launch of the day, 5 sec start-up. Restarted PC, launch Houdini, 1min 50 start-up. Only difference between the two is installing license on new build.
UPDATE v2: Now using a new Win10 system with SSD drives, the start-up time is consistently fast.
I do have a hybrid setup so that does make sense and I've experienced the same in other software too.
Three things confused me enough to ask the initial question…
1. The quick start-up when launching new builds. Next time I update to a new build, I'll make sure to restart pc before I launch to confirm.
2. I was positive the start-up time for early H14 builds was very quick. (or much quicker than 1min 45)
3. I remember seeing a bug fix in the Journal for slow start-up time and wondered if the bug had resurfaced.
I could be wrong on all the above as I'm relying on my memory, which is not so reliable.

I know the answer to the next question will vary a lot depending on system setup but what is the expected start-up time for Houdini on a HDD? There's quite a big gap between 4 sec and 1min 45 so if I know a ballpark figure of where it's supposed to be, I can either stop worrying or dive deeper.
I've also found that when I try clearing the cache in Houdini, it doesn't release the RAM so I need to restart Houdini. Restarting Houdini when this happens also causes the long start-up. (the cache is overwritten?) Is there is a way for me to control how Houdini uses memory for sims so it doesn't overwrite the cache used for the “quick launch”.
Rob
UPDATE: Confirmed odd behaviour. Installed new build, first launch of the day, 5 sec start-up. Restarted PC, launch Houdini, 1min 50 start-up. Only difference between the two is installing license on new build.
UPDATE v2: Now using a new Win10 system with SSD drives, the start-up time is consistently fast.
Edited by robsdesign - July 4, 2016 05:47:56
Technical Discussion » Start-up time
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- robsdesign
- 236 posts
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Hi, I'm having a minor issue that I'd like to fix regarding start-up time for Houdini Indie.
On each new build, when I first launch Houdini, the start-up time is normal. (around 4 seconds)
Afterwards, When I launch Houdini for the first time, (ie.next day) the start-up is around 1min 40sec (yeh, I timed it). However, if I close and relaunch it's back to 4 seconds.
One of the things I like about Houdini is the fast start-up but every day, the first launch is much longer than I expect it to be.
Does anyone else have this issue and know of a fix? I would accept it as normal behavior if Houdini didn't start-up in 4 seconds on each new build. (making me think it's been fixed and then disappointing me the next day)
However, I have a feeling it could be my setup as I'm also having issues with “Error running Python code to access the help manager”. I'm wondering if the two are related and if I can fix one of the issues, the other might be fixed too.
Both issues started around the more recent H14 builds and persist with H15.
Rob
On each new build, when I first launch Houdini, the start-up time is normal. (around 4 seconds)
Afterwards, When I launch Houdini for the first time, (ie.next day) the start-up is around 1min 40sec (yeh, I timed it). However, if I close and relaunch it's back to 4 seconds.
One of the things I like about Houdini is the fast start-up but every day, the first launch is much longer than I expect it to be.
Does anyone else have this issue and know of a fix? I would accept it as normal behavior if Houdini didn't start-up in 4 seconds on each new build. (making me think it's been fixed and then disappointing me the next day)
However, I have a feeling it could be my setup as I'm also having issues with “Error running Python code to access the help manager”. I'm wondering if the two are related and if I can fix one of the issues, the other might be fixed too.
Both issues started around the more recent H14 builds and persist with H15.
Rob
Technical Discussion » Error running Python code to access the help manager
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- robsdesign
- 236 posts
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Hi, I have some updated information on this issue, not sure if it will help diagnose the problem.
The F1 help for the shelf tools launches the help browser and works as intended. F1 help for anything else, doesn't work.
Rob
The F1 help for the shelf tools launches the help browser and works as intended. F1 help for anything else, doesn't work.
Rob
Technical Discussion » REFLECTION ROUGHNESS ISSUE
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- robsdesign
- 236 posts
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Hi, what build of Houdini are you using? There was a bug with the mantra surface shader's roughness (when set to exactly 0.3) but it's been fixed in the latest build. (15.0.393)
I agree with Carlo_C above, the Principled Shader is good option but as I use a metal/roughness workflow, I have some issues with them both…
The Mantra Surface Shader doesn't really work with a Metal/Roughness texturing workflow.
The Principled Shader doesn't display metallic materials properly in the OpenGL Viewport.
Both of these issues relate to the Metallic (mantra setting or Principled preview) using specular colour/maps instead of diffuse maps.
To answer your initial question, if you are using an older build, ignore the bugged 0.3 roughness results and work with any other values. ie. Bugged 0.3 is the same as 0 roughness. Your 0.300001 result is correct so in-between the two is 0.15 roughness.
Hope that helps
Rob
I agree with Carlo_C above, the Principled Shader is good option but as I use a metal/roughness workflow, I have some issues with them both…
The Mantra Surface Shader doesn't really work with a Metal/Roughness texturing workflow.
The Principled Shader doesn't display metallic materials properly in the OpenGL Viewport.
Both of these issues relate to the Metallic (mantra setting or Principled preview) using specular colour/maps instead of diffuse maps.
To answer your initial question, if you are using an older build, ignore the bugged 0.3 roughness results and work with any other values. ie. Bugged 0.3 is the same as 0 roughness. Your 0.300001 result is correct so in-between the two is 0.15 roughness.
Hope that helps
Rob
Technical Discussion » Error running Python code to access the help manager
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- robsdesign
- 236 posts
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I had the same problems with both the tooltips and F1 Help when I upgraded from 14 to 15. These issues remained until I installed 15.0.393 where the tooltips now work but F1 Help still doesn't. (produces same error as in the 2nd screenshot in the original post)
I did do a clean install this time (whereas I usually overwrite) so I'm not sure if a clean install or 393 itself fixed the tooltip problem.
Note: I can still use the Help browser after clicking the “home” button, it's the F1 Help page linking that doesn't work. So I have to search for the page I wanted, which isn't ideal.
Win 7 x64,
Houdini Indie 15.0.393
I did do a clean install this time (whereas I usually overwrite) so I'm not sure if a clean install or 393 itself fixed the tooltip problem.
Note: I can still use the Help browser after clicking the “home” button, it's the F1 Help page linking that doesn't work. So I have to search for the page I wanted, which isn't ideal.
Win 7 x64,
Houdini Indie 15.0.393
Houdini Lounge » Mantra surface shader metallic setting
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- robsdesign
- 236 posts
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Thank you very much, I appreciate the help. 
Seems so simple when I look at it. I had looked inside before but totally missed that the “Of” opacity was already in the Principled Shader's Compute Lighting and it basically just needed a texture node plugged into it.
thanks
Rob

Seems so simple when I look at it. I had looked inside before but totally missed that the “Of” opacity was already in the Principled Shader's Compute Lighting and it basically just needed a texture node plugged into it.
thanks
Rob
Houdini Lounge » Mantra surface shader metallic setting
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- robsdesign
- 236 posts
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Thanks for the reply and the link.
Part of the issue is that I needed to use opacity maps for holes in the metal. (ie. old rusty metal)
I use Substance Painter for texturing which allows me to work in either metal/roughness or spec/gloss. So, to work with opacity and metal/roughness… In Photoshop, I needed to invert the metallic map, apply it as a mask on a white layer with the diffuse underneath so I can apply it as specular map in Houdini. (for multiple textures)
I love Houdini for it's non-destructive workflow. The Principled shader works perfectly with Substance Painter export, allowing me to quickly update textures and test results but it lacks opacity maps. The Mantra Surface shader works as expected, apart from the need to create a specular map for a metal/roughness workflow. (which is where I'm confused)
I assumed that there must be a better method of using the Mantra Surface shader in a metal/roughness workflow so I guess my questions are (in order);
1) Is the Mantra Surface shader meant to work in a Metal/Roughness workflow or not?
2) If so, should I send a bug report for the metallic setting to be fixed?
3) If not, is it possible for me to modify it so it will work?
4) If not, is it possible to modify the Principled Shader to include opacity maps?
Thanks
Rob
Part of the issue is that I needed to use opacity maps for holes in the metal. (ie. old rusty metal)
I use Substance Painter for texturing which allows me to work in either metal/roughness or spec/gloss. So, to work with opacity and metal/roughness… In Photoshop, I needed to invert the metallic map, apply it as a mask on a white layer with the diffuse underneath so I can apply it as specular map in Houdini. (for multiple textures)
I love Houdini for it's non-destructive workflow. The Principled shader works perfectly with Substance Painter export, allowing me to quickly update textures and test results but it lacks opacity maps. The Mantra Surface shader works as expected, apart from the need to create a specular map for a metal/roughness workflow. (which is where I'm confused)
I assumed that there must be a better method of using the Mantra Surface shader in a metal/roughness workflow so I guess my questions are (in order);
1) Is the Mantra Surface shader meant to work in a Metal/Roughness workflow or not?
2) If so, should I send a bug report for the metallic setting to be fixed?
3) If not, is it possible for me to modify it so it will work?
4) If not, is it possible to modify the Principled Shader to include opacity maps?
Thanks
Rob
Houdini Lounge » Mantra surface shader metallic setting
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- robsdesign
- 236 posts
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Hi,
I probably wasn't clear enough in my description so I've added some visual information and corresponding Houdini file.
I've shown that using a base/diffuse colour of red and setting the Squares.jpg texture as the Metallic map produces different results between the two shaders.
Ideally, I'd like to either;
a) Modify the Mantra Surface Shader metallic setting to behave like the Principled Shader.
b) Modify the Principled Shader to include Opacity Maps.
I am new to Houdini so although I am aware that I could dive in and modify them myself, I would appreciate any help that would make that process a little easier for me.
Thanks
Rob
I probably wasn't clear enough in my description so I've added some visual information and corresponding Houdini file.
I've shown that using a base/diffuse colour of red and setting the Squares.jpg texture as the Metallic map produces different results between the two shaders.
Ideally, I'd like to either;
a) Modify the Mantra Surface Shader metallic setting to behave like the Principled Shader.
b) Modify the Principled Shader to include Opacity Maps.
I am new to Houdini so although I am aware that I could dive in and modify them myself, I would appreciate any help that would make that process a little easier for me.

Thanks
Rob
Houdini Learning Materials » Houdini and Substance Painter
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- robsdesign
- 236 posts
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I've also been using Substance Painter with Houdini. I haven't used the custom shelf tool posted above as using the fbx export worked for me.
It's a very similar process to the above;
- Group your geos into the material sets
- Use a material sop to set the materials
- Export as FBX
Importing the FBX into Substance Painter creates texture sets from the material sets. I don't know if the shelf tool does something extra/differently but this method works for me.
Rob
It's a very similar process to the above;
- Group your geos into the material sets
- Use a material sop to set the materials
- Export as FBX
Importing the FBX into Substance Painter creates texture sets from the material sets. I don't know if the shelf tool does something extra/differently but this method works for me.
Rob
Houdini Indie and Apprentice » Rain tool in Orbolt
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- robsdesign
- 236 posts
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I'm glad to be of any help, I'm very new to Houdini myself.
I was experimenting a lot during the project and accidently left that V point attribute on. (It's not needed) Sorry for the confusion.
V comes from the VFX rain node. (Velocity) If you middle click on the node, you can see details including the point attributes. I didn't add anything extra so it should be there as default.
My main purpose for using these two nodes is to create velocity trails with the vdb and then skin them into polys. It suited my needs but I expect there are ways to take it further or do it better with a completely different method.
Rob
I was experimenting a lot during the project and accidently left that V point attribute on. (It's not needed) Sorry for the confusion.
V comes from the VFX rain node. (Velocity) If you middle click on the node, you can see details including the point attributes. I didn't add anything extra so it should be there as default.
My main purpose for using these two nodes is to create velocity trails with the vdb and then skin them into polys. It suited my needs but I expect there are ways to take it further or do it better with a completely different method.
Rob
Houdini Indie and Apprentice » Rain tool in Orbolt
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- robsdesign
- 236 posts
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Hi, I used this asset recently and the way I rendered it was to add the “vdb from particles” node, the “convert vdb” node and use the “basic liquid material” from the gallery.
There is probably other ways to do this but it worked for what I needed. I've added a screenshot for the settings I used on the nodes but you'll need to see what works for you.
Rob
There is probably other ways to do this but it worked for what I needed. I've added a screenshot for the settings I used on the nodes but you'll need to see what works for you.
Rob
Houdini Lounge » Mantra surface shader metallic setting
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- robsdesign
- 236 posts
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Hello everyone,
I have a quick question regarding the Mantra Surface shader and Metal/Roughness workflow.
Is the Mantra Surface shader Metallic Map intended to act the same way as the Metallic Map in the Principled Shader, allowing a Metal/Roughness workflow?
From what I can see in the Mantra Surface, the metallic setting is reflecting the specular colour not the diffuse colour, resulting in the need for a specular map.
Compared to the Principled shader where the metallic setting it reflecting the diffuse colour. (which is what I expect for a metal/roughness workflow)
It's most likely user error so I appreciate any help I can get from more experienced users. Apologies if this has already been answered elsewhere.
Thanks
Rob
I have a quick question regarding the Mantra Surface shader and Metal/Roughness workflow.
Is the Mantra Surface shader Metallic Map intended to act the same way as the Metallic Map in the Principled Shader, allowing a Metal/Roughness workflow?
From what I can see in the Mantra Surface, the metallic setting is reflecting the specular colour not the diffuse colour, resulting in the need for a specular map.
Compared to the Principled shader where the metallic setting it reflecting the diffuse colour. (which is what I expect for a metal/roughness workflow)
It's most likely user error so I appreciate any help I can get from more experienced users. Apologies if this has already been answered elsewhere.
Thanks
Rob
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